Backfire Into Intake On Acceleration
 

2.3L 92 Ranger 137k miles
No tag so can't test drive it on the highway.

Idles well.
Bogs down often but not always when you give it gas.
Backfires sometimes into intake when you give it gas.

Any thoughts?

Probably a bad/fouled MAF sensor, or could be a vacuum leak. Doesn't narrow it down that much.

Maybe a spark or cam timing issue, or srticking intake valves.

With the mileage on the vehicle, it's time for a new cam belt & with the mileage, intake valve carbon deposits also belong on your suspect list, especially if it's using some oil.

So maybe begin with a cyl balance test, followed by a compression check on at least the & suspect cyl's the balance test has flagged, if not on all 4 cyl's.

Let us know what you find.

Thanks for the replies guys. I haven't done anything with it yet but I'll look into the tests you guys mention.

Two other things:
1) It has had like 2 periods where it sat outside for 6 months straight without being started. Maybe even a year one time.
2) If I pump the gas peddle, I can get it to accelerate higher without bogging down. I have to finesse it really. Pump the peddle slightly until it starts to bog, let go, pump a little more... and each time you can increase the RPM until eventually it's high enough to put into gear.

When it was stored, was fuel stabilizer added at the pump, before filling up & was the engine run long enough to distribute the stabilizer through out the fuel system????

Check fuel filter and fuel pressure.

No, nothing of the sort. And come to think of it, it ran fine before the periods it sat. It sat through winter too. But I'm here in FL, so maybe not too bad?

Yeah I was thinking about that but then why the backfire? But I will check the pressure.

is the mil light on? Are you able to read the codes to see if any got thrown

The mil light is off. I just got a code reader and will see if anything comes up.

I wanted to retry describing the symptoms again.

If I give it gas slowly it will rev up without bogging down or backfiring into manifold.
If I give it gas quickly it will bog down and sometimes backfire into manifold.

Imho you need to do a fuel pressure test also you can pull the vacuum line off the fuel pressure regulator and see if there is gas in it

I pulled the vacuum line off and I didn't see any gas in it. There was also no change in how the vehicle runs or accelerates with the vacuum line off. Meaning no change in performance/or lack thereof.

Scanner shows passed. There were two codes in memory for the MAF sensor though. But that could be from older problems.

Sounds like a lean condition definiatley check fuel psi filter ect. but might also be a cloged cat or muffler/exhaust

I think when you pull the vacuum line of there should be some change when you drive I think you might have found your issue. Did you check that there was vacuum. You should do a FP test. Let's see what the other peeps say.

Well I can't drive the vehicle since it has no tag but in terms of idle and acceleration there was no difference with the vacuum line off the fuel pressure regulator. And yes there is vacuum.

I'm about to head up to autozone to rent the fuel pressure tester.